Air Jet Impingement Baking of Bread: Heat-Mass Transfer Dynamics and Process Optimization.

Abstract

Air jet impingement baking is a high-intensity convective heating technology that enhances heat transfer efficiency by reducing thermal boundary layer resistance at the product surface. This study investigated the application of air jet impingement to bread baking, a volumetric food system with complex heat and mass transfer dynamics. Baking experiments were conducted at varying oven temperatures (165-195°C), air velocities (12-15 m/s), baking times (15-35 min), and tray positions using a central composite rotatable design. Product quality and process efficiency were evaluated through moisture content, height change, bulk density, bread volume, crust thickness, hardness, color parameters (a*, BI), springiness, hydroxymethylfurfural (HMF) formation, and energy consumption. Results indicated that temperature and baking time were the primary factors influencing structural development, browning, and HMF formation, whereas air velocity had a limited direct effect on most quality attributes. The intensified convective heat transfer in the impingement system accelerated surface heating and crust formation, achieving comparable or improved bread volume and texture at shorter baking times relative to conventional convection baking. Optimization analysis identified 195°C, 13.32 m/s air velocity, 35 min baking time, and lower tray position as the optimum conditions, providing balanced crust formation, desirable textural properties, and reduced energy consumption. Overall, air jet impingement baking demonstrates potential as an efficient alternative to conventional oven baking, improving heat transfer performance while maintaining product quality and minimizing formation of heat-induced processing contaminants.